1. Field of the Invention
This invention relates to a power thyristor and a method of fabricating a power thyristor having at least three electrodes arranged on the cathode-base zone thereof, where one electrode serves as a control or gate electrode, and where one electrode (generator gate) next to the control gate serves for drawing a current and the other electrode serves as a supplementary firing electrode (firing gate).
2. Description of the Prior Art
Thyristors of the type mentioned above are known, e.g. from DE-OS No. 21 46 178. In these known components the thyristors include an amplifying gate for internal reinforcement of firing. In order to obtain uniform firing over the entire thyristor surface, firing gates are provided on the cathode-side surface which are controlled by the amplifying gate (auxiliary thryistor) acting as a generator gate. These known thyristors have several following disadvantages. Firstly, if the anode current of a fired thyristor drops, the current in the thyristor is no longer uniformly distributed over the entire cathode surface, but flows only at certain places. Secondly since the auxiliary thyristor itself does not fire at the very low anode voltage of the fired thyristor (.ltoreq.2 V), firing does not occur in the region of the firing gate when a rise in anode current is experienced. The current then arising locally in the thyristor can lead to distruction of the component.
In order to achieve a uniform firing distribution it is further known to increase the area of the control electrode, or to increase the thyristor emitter edge-length. Such measures, however, have as a consequence the necessity of very high firing currents.